Prostojov Club/team, Miroslav Cersonek, Czech Cabal; that's your answer!!
I'm not sure if you realize this. But every player you and Jack mentioned, passed through Prostejov, Cersonek, or one of his sponsored events.
Czech's appear to be very nationalist and proud of their Tennis players and history. And Cernosek (and his programs, events and affiliations) feeds into [this], and doesn't discourage it.
Repeat: Every player you mentioned (including Safarova and Berdych; Hingis and Stepanek), and one's you didn't--like Adam and Petra; were affiliated with, met via him in one way or the other.
Everything just appears so inbred to many outsiders (and it's not just because these players are around each other a lot, in the same sport). I think he likes it that way. He damn sure doesn't appear to discourage it (otherwise, he wouldn't mind them leaving). 'Keep it in the [Cernosek, and/or Czech] family', seems to be his motto.
Jack; correct me if I'm wrong on anything (and not cause you disagree, don't want to believe it).
PS: I'm only writing this, cause I think many Petra fans continue to be unaware of the gigantic influence this guy has on her, and other Czech players, in varying degrees, one way or the other.